1. Field of the Invention
The present invention relates to a paper supply device and an image forming apparatus using the paper supply device, and more particularly to a paper supply device that switches between plural types of sheets for use thereof and an image forming apparatus using the paper supply device.
2. Description of the Related Art
Ordinarily, in printers and the like, sheets on which an image is to be formed are housed in a cassette or magazine that is loaded into an apparatus body such that the cassette or magazine can be freely pulled out. The sheets are removed one sheet at a time by a feeding mechanism disposed in the apparatus body and fed to an image forming section, where image formation is conducted.
With respect thereto, image forming apparatus have been devised which are disposed with a tray that is exposed to the outside of the apparatus body and is for manually feeding the paper. That is, when the use of plural types of sheets is required of the image forming apparatus, the image forming apparatus includes a paper supply device disposed separately from the aforementioned cassette or magazine. The paper supply device includes: a sheet housing in which are stacked and which houses plural types of sheets; and feeding means for feeding, to the image forming section within the image forming apparatus, the sheets stacked and housed in the sheet housing.
For example, a paper supply cassette has been proposed where a second sheet feeding device is disposed on the end portion at the pullout side of a cassette that is loaded into the apparatus body such that the cassette can be freely pulled out. The second sheet feeding device includes: a second sheet housing separate from the sheet housing of the cassette; and feeding means that feeds the sheets housed in the second sheet housing to the image forming section (e.g., see Japanese Patent Application Publication (JP-A) No. 2001-225973).
However, when feeding means is attached to a cassette that can be freely pulled out as described above, it is necessary to dispose, in the cassette, drive means for driving paper supplying means, or to dispose, in the apparatus body, the drive means for driving the paper supplying means and to dispose, in the cassette and the apparatus body, drive coupling means for transmitting the driving force of the drive means to the paper supplying means, which results in an increase in the cost of the cassette and complication of the apparatus.
Further, because the paper supply cassette is frequently loaded and unloaded by a user, the weight of the paper supply cassette increases and its operability becomes poor when the drive means is disposed in the cassette, and there is the potential for malfunction when the drive means is disposed in the apparatus body.
An image forming apparatus has also been proposed which includes: a paper supply cassette that has a first sheet housing and is configured such that the paper supply cassette can be freely loaded into and unloaded from the image forming apparatus; and a second sheet housing disposed separately from the paper supply cassette. The paper supply cassette can itself be loaded into and unloaded from the image forming apparatus, and the second sheet housing can be pulled out together with the paper supply cassette while leaving in the apparatus body a paper supply roll that conveys the sheets housed in the second sheet housing (e.g., see JP-A No. 11-343037).
However, in this configuration, because the paper supply cassette and the second sheet housing are disposed separately, it is necessary to dispose in the image forming apparatus a mechanism for loading and unloading just the paper supply cassette itself and a mechanism for loading and unloading the second sheet housing together with the paper supply cassette. Thus, not only does the structure become complicated, but the apparatus itself also becomes large.
Further, when just the paper supply cassette itself is loaded and unloaded, and when the paper supply cassette and the second sheet housing are together loaded and unloaded, the position of the paper supply roll cannot be sufficiently lowered because the paper supply roll becomes an obstacle, the height of the paper supply device increases, and it is difficult to make the overall apparatus compact.